From U.S. Pat. No. 6,129,066 it is known, for example, in a combustion engine, to provide a piston for a four-valve arrangement with a recess, which is approximately in the center relative to the arrangement of a cylinder spark plug in the cylinder head. The recess further has in the piston a flat geometry and is, in particular, round. Such a piston geometry should be in the position, on the one hand, to reduce the tendency to knock and, on the other hand, should allow improved lean operation with reduced HC emissions. In particular, such a system should be usable for auto-ignition combustion engines.